The FM-CW principle is known, or the pulse principle are described in detail by Merril Skolnik in "Introduction to Radar Systems", McGraw-Hill, (1980), page 68 ff.
Range measurements of the this type have been used, for example, in measuring the altitude of aircraft over large distances (See, for example, German Patent Publication DE-C 3.830.992 "Aircraft Radar") and in the so-called very short range (0 to approximately 30 m) for liquid level measurements in process containers and storage tanks (See German Patent Publication DE-B 2 129 290 and PCT Publication WO 92/14 124).
A common feature of these applications is the difficulty of punctiform range measurements between the transceiver unit characteristic of the method and a so-called measuring spot or point on the surface of the objected to be measured. This measuring spot is very small in comparison with the transceiver antenna. The FM-CW principle has not been transferred to applications in which a comparatively small measuring spot is defined in order to carry out, for example, range measurements in relation to individual contour points on a non-flat surface of an object.